Last 12 month's average

Hi simonlblea

Try the Index & Match (Non volatile)

Formula:

=AVERAGE($A3:INDEX(3:3,MATCH("Rolling average",$1:$1,0)-1))

Or

Formula:

=AVERAGEIF($A3:INDEX(3:3,MATCH("Rolling average",$1:$1,0)-1),">0")

If you need to exclude zero values when averaging.